Construction of pipelines in the open trench usually causes a negative impact on the city routine: ground works impact road traffic, trees and sometimes even buildings have to be removed. The best alternative for the open trench method are non-trench construction methods. Although trenchless method could be more expensive than open trench construction, the savings in resurfacing and landscaping can be substantial, and the ability to avoid traffic disruption makes trenchless method a better choice.
For gravity sewer and storm sewers, when it is necessary to ensure a slope without deviations from the project, as well as for casings for any communications, SIA “Norma-S” uses the microtunneling method with a German-made AVN machine. Communications are built from CC-GRP pipes, ceramics or polymer concrete DN400 to DN1700 mm.
When constructing a pipeline using a microtunnel method, it is necessary to build two shafts for one section: one, large in size, is a reinforced concrete chamber or well up to 6 m in diameter, where microtunnel equipment is installed, the second, smaller one is a chamber or well up to 4 meters in diameter, where the head of the microtunnel machine is dismantled and separate sections of the pipeline are connected. From one large shaft it is possible to carry out microtunneling in several directions — both two sections of the main pipeline, and connections on the sides. Wells are built using the submersible method: first, the first level of the well is constructed, soil is removed from it, the well is immersed in the ground, and the next level is constructed on top until the desired depth is reached.
After the construction of the wells, the installation of a microtunnel complex is carried out: a pushing frame is installed in the starting well, the head (drill) of the microtunnel is installed, containers to provide control of the complex, supply pressure and lubricant — bentonite are placed near the well . With the start of drilling, the head of the microtunnel machine cuts into the ground, and pipes are gradually fed from the starting well with the help of a pushing frame. With each pipe, head control cables and hoses are added, to supply bentonite and remove a mixture of worked-out soil and water.
When the head of the microtunnel reaches the receiving well, the head is dismantled and the complex is ready for laying the next section.